Method and system for monitoring control rod element assembly position

Abstract

Compliance with administrative limits on cumulative exposure of control rod groups in the reactor core, is monitored by computing the incremental effective exposure for each group commensurate with core power, for each time increment at which each group is within the position range where an administrative limit is imposed. The increments of effective exposures for each group are accumulated, and the accumulated effective exposure for each group is compared with the administrative limit to each group. This comparison is then displayed to the reactor operator, preferably using either a “rolling wheel” or “sliding bar” format.

What is claimed is:  
     
       1. In a pressurized water nuclear power plant having a nuclear reactor core and a multiplicity of control rods arranged as groups for movement sequentially through the core for controlling the reactor power while exposed to the nuclear reactions in the core, a system for the operator to monitor compliance with administrative limits on the cumulative exposure in the core of the control rod groups, comprising: 
       means for measuring the core power and generating a power signal commensurate therewith;  
       means for measuring the position of each control rod group in the core;  
       means for establishing an incremental time base common to the measuring of the core power and the measuring of the position of each group;  
       means responsive to said means for measuring of position, for determining when on said time base, each group is within said position range;  
       means for determining the core power when each group is in said position range;  
       means for computing an incremental effective exposure for each group, commensurate with core power, for each time increment at which each group is within said position range;  
       means for accumulating said incremental effective exposure for each group;  
       means for comparing the accumulated effective exposure for each group with the administrative limit for each group; and  
       means for displaying said comparison to the reactor operator.  
     
     
       2. The system of claim  1 , wherein said administrative limit is in the form of a limit index defined by a maximum permissible hours of accumulated effective exposure during a reference period of exposure; and 
       said means for displaying include at least one scale of uniform intervals, marked with a plurality of numeric values indicative of an initial zero value and a final valve corresponding to the reference period;  
       an indicator configuration for each group, each indicator configuration having a scale associated therewith, and consisting of an indicator for each component of actual exposure, each indicator initially appearing at the zero representation of the scale and growing in size toward said final value to span the number of scale intervals corresponding to the ratio of effective exposure of the component to the reference period;  
       means for advancing each indicator along said scale toward the said final value, at a uniform rate, independently of but simultaneously with said indicator growth.  
     
     
       3. The system of claim  2 , wherein 
       each of said scales is displayed for a respective group, in the form of a circle with coincident zero and said final value; and  
       each display of an indicator of a component is a sector of the circle, said sector having a variable angle and which advances by continually rotating about the center of the circle toward said final value.  
     
     
       4. The system of claim  2 , wherein 
       one scale is a linear segment with the zero value at one end and said final value at the other end;  
       the indicator configuration for each of at least two groups is associated with said one scale; and  
       each indicator of a component is displayed as a horizontal bar, which grows by increasing in horizontal length and which advances by continually moving horizontally toward said final value.